Monitoring and diagnosing the status of rotating and reciprocating machinery start with accurate and dependable measurements from a transducer and associated electronics and then proceed to other sophisticated analyzing apparatus for reduction and display. One such transducer is a proximity transducer which may be utilized for, inter alia, monitoring the vibration characteristics of a rotating shaft of a machine. In this environment, the transducer must operate under very adverse physical, chemical and mechanical conditions and it is often very difficult to replace such transducers. Thus, there is an ongoing effort to make the proximity transducer one of the most reliable parts of the monitoring system.
Typically, the proximity transducer, in conjunction with associated electronics, outputs a signal correlative to the spacing between an object or "target" (the rotating shaft of the machine) and a sensing coil of the proximity transducer. It is critical that the length or spacing between the "target" and the sensing coil of the proximity transducer remains within the linear range of the transducer for providing accurate and reliable measurements when in operation. Presently, one recurring problem involves producing transducers all of which have similar characteristics so that they can be interchangeable without inordinate, time-consuming calibration.
In addition, the proximity transducer should be able to endure the mechanical, physical and chemical aggression from the surrounding environment. Thus, the hallmark for providing accurate and reliable measurements relies on precision and quality parts and method of manufacturing to form a transducer which is impervious to the predations of the environment and which does not consume an inordinate amount of the linear range of the transducer.
The following prior art reflects the state of the art of which applicant is aware and is included herewith to discharge applicant's acknowledged duty to disclose relevant prior art. It is stipulated, however, that none of these references teach singly nor render obvious when considered in any conceivable combination the nexus of the instant invention as disclosed in greater detail hereinafter and as particularly claimed.
______________________________________ U.S. PATENT DOCUMENTS DOCUMENT NO. DATE NAME ______________________________________ 2,361,348 October 24, 1944 Dickson et al. 2,890,505 June 16, 1959 Brand 3,932,828 January 13, 1976 Plunkeu et al. 4,000,877 January 4, 1977 Shead et al. 4,162,138 July 24, 1979 Byrne 4,377,548 March 22, 1983 Pierpont 4,408,159 October 4, 1983 Prox 4,419,646 December 6, 1983 Hermle 4,470,786 September 11, 1984 Sano et al. 4,680,543 July 14, 1987 Kohen 4,829,245 May 9, 1989 Echasseriau et al. 4,954,307 September 4, 1990 Yokoyama 4,959,000 September 25, 1990 Giza 5,016,343 May 21, 1991 Schutts 5,018,049 May 21, 1991 Mehnert 5,021,737 June 4, 1991 Schutts 5,039,942 August 13, 1991 Buchschmid, et al. 5,049,055 September 17, 1991 Yokoyama 5,122,046 June 16, 1992 Lavallee et al. 5,133,921 July 28, 1992 Yokoyama 5,138,292 August 11, 1992 Forster 5,147,657 September 15, 1992 Giza 5,151,277 September 29, 1992 Bernardon, et al. 5,182,032 January 26, 1993 Dickie et al. 5,226,221 July 13, 1993 Kilgore 5,240,397 August 31, 1993 Fay et al. 5,252,051 October 12, 1993 Miyamoto et al. 5,351,388 October 4, 1994 Van Den Berg, et al. 5,376,325 December 27, 1994 Ormson ______________________________________ FOREIGN PATENT DOCUMENTS DOCUMENT NO. DATE COUNTRY ______________________________________ UK 1 313 748 April 18, 1973 Great Britain UK 1 353 603 May 22, 1974 Great Britain JA-139710 August 6, 1978 Japan WO 84/03794 September 27, 1984 PCT FR 2576-245-A July 25, 1986 France JA 6-37130-A October 2, 1994 Japan ______________________________________
The two patents to Schutts and the patent to Van Den Berg, et al. reflect assignee's ongoing commitment to providing an accurate sensor which is impervious to predations of the environment.
The French patent to Jaeger teaches the use of a method and apparatus for injection molding of an elongated detector with a sensor at one end. One end of the detector is supported by the mold while the sensor end is engaged by a centering sleeve (130). The centering sleeve (130) terminates in a piston (132) which is mobile in a cylinder (126) and slides about a fixed rod (138). Thermoplastic is injected into the mold and the centering sleeve is removed from the sensor when the injection process is only partially complete.
The Japanese patent to Kawakami teaches the use of sealing a semiconductor chip by transfer molding. A semiconductor chip (4) is mounted on a carrier (1) and is held at a fixed position via mobile pins (17) and (18). The mobile pins (17) and (18) are movably fitted to a top force (11) and a bottom force (12) for freely advancing or retracting the pins into and out of the cavities (15) and (16). While the pins (17) and (18) are in contact with the carrier (1), a resin (20) is injected into the cavities (15) and (16) through gates (13) and (14) and the pins (17) and (18) are gradually retracted in accordance with the injecting state of resin (20).
The patent to Yokoyama teaches the use of an apparatus for manufacturing plastic encapsulated electronic semiconductor devices. A support pad (11) is firmly fixed by first and second sliders (24A) and (24B) and also by mold halves (19) and (20). The first and second sliders (24A) and (24B) are moved outwardly of a cavity (25) when the cavity is half filled with the plastic encapsulating material. Spaces, which are formed after movement of the sliders, are filled with the plastic encapsulating material directly poured through a gate (23). It should be noted that the sliders (24A), (24B) perform two functions in the cavity (25). The first function is to firmly grasp a thin end portion of the support pad (11) thereby fixing same in position and the second function is to narrow a passage through the gate (23).
The patent to Pierpont teaches the use of a method for encapsulating an electrical component having radial leads. A large multi-cavity mold is loaded with a plurality of horizontal radially leaded capacitors. The closed mold grips the leads (15). A top pin (25) pushes each component body downward a predetermined degree so that each body is left in about the same position within the corresponding mold cavity. A bottom pin (28) then pushes each component body upwardly only slightly above a center of the mold cavity so that upon bottom pin withdrawal, stresses within the lead wires of the electrical component cause the component bodies to spring back just to the mold cavity center portion. Molding resin is then introduced.
The other prior art listed above, but not specifically discussed, teach other sensor devices and molding processes and further catalog the prior art of which the applicant is aware. These references diverge even more starkly from the references specifically distinguished above.